Process icing sugar and almond meal in a food processor until finely ground, triple-sift into a large bowl and set aside. Whisk egg white in an electric mixer until soft peaks form (1-2 minutes).

Add caster sugar, a tablespoon at a time, whisking continuously until incorporated and mixture is thick and glossy (2-3 minutes), then add food colouring. Stir in almond mixture in batches until incorporated and mixture slowly slides down sides of bowl when bowl is tilted.